The present invention generally relates to a cryogen deflashing apparatus and, more specifically, to a cryogen deflashing apparatus adapted to rapidly remove residual flash from molded articles.
Molded articles often have thin pieces of unwanted material extending therefrom called "flash" which must be removed for the articles to reach their desired final configuration. Removing flash from articles formed from flexible materials such as rubber, plastics, and the like, is difficult in view of the soft, elastic nature of flexible materials. While various types of mechanical trimming operations have been proposed for removing unwanted flash, these methods have proven to be uneconomical in a number of applications.
In order to both simplify and reduce the cost of flash removal, various attempts have been made to freeze or otherwise cool the articles in order to embrittle the thin sectioned flash, whereafter the embrittled flash is broken-off, trimmed, or otherwise removed. Some of these methods utilize a two-stage process wherein the workpieces are cooled in a first stage to effect flash embrittlement and then vibrated, tumbled, or otherwise mechanically treated in a second stage to break away the embrittled flash. One approach is to use a cryogen material, such as liquid nitrogen, to effect embrittlement of the workpiece flash. As utilized herein, the term "cryogen" will be understood to refer broadly to fluids which are at temperatures of about -60.degree. F. and below.
Two-stage processes, however, are undesirable from several viewpoints. They are time consuming to carry out because cooling the workpieces and removing their flash comprise separate steps that are carried out sequentially rather than concurrently. Because the workpieces are cooled only once and will not be cooled again at other stages of the flash removal procedure, adequate time must be devoted at the outset to providing a thorough cooling of the workpieces to assure that they are refrigerated to an extent that their flash will remain embrittled throughout the remainder of the flash removal process. Sometimes the extensive degree of refrigeration which is required results in the generation of undesirable stresses and/or the formation of cracks or other types of structural defects in the workpieces. An equally troubling drawback of the two-stage processes is that, when there is a relatively large quantity flash to be removed, the workpieces may not remain adequately embrittled during the entire time required for deflashing. Where such is the case, the workpieces are not properly deflashed.
These drawbacks have been overcome by shot blast deflashing machinery which operate with a single flash embrittling and removing stage. For example, see U.S. Pat. Nos. 4,519,812, 4,598,501, 4,646,484, and 4,648,214 and U.S. patent application Ser. No. 08/542,447, filed Oct. 12, 1995, the disclosures of which are expressly incorporated herein in their entirety by reference. While such machinery performs in an exemplary manner, there is a never ending desire to decrease the required time and/or cost of a deflashing operation. Accordingly, there is a need in the art for an improved cryogen shot-blast deflashing machine which more rapidly removes residual flash from molded articles and/or for means of converting existing deflashing machines, in a cost effective manner, to more rapidly remove residual flash from molded articles.